Find the sum of all multiples of 2 and 5 below N | C # program to find the sum of all multiples of 2 and 5 below N ; Function to find sum of AP series ; Number of terms ; Function to find the sum of all multiples of 2 and 5 below N ; Since , we need the sum of multiples less than N ; Driver code
using System ; public class GFG { static long sumAP ( long n , long d ) { n /= d ; return ( n ) * ( 1 + n ) * d / 2 ; } static long sumMultiples ( long n ) { n -- ; return sumAP ( n , 2 ) + sumAP ( n , 5 ) - sumAP ( n , 10 ) ; } static public void Main ( ) { long n = 20 ; Console . WriteLine ( sumMultiples ( n ) ) ; } }